The present invention relates to footwear, more particularly to an athletic shoe having a stabilizing frame for flexibly decoupling heel and forefoot portions of the shoe from each other, preferably along a longitudinal axis passing substantially through the cuneiform bones of a wearer, while fully supporting a foot along its entire length.
The modem athletic shoe is a highly refined combination of many elements which have specific functions, all of which work together for the support and protection of the foot. Athletic shoes today are as varied in design and purpose as are the rules for the sports in which the shoes are worn. Tennis shoes, racquetball shoes, basketball shoes, running shoes, baseball shoes, football shoes, walking shoes, etc. are all designed to be used in very specific, and very different, ways. They are also designed to provide a unique and specific combination of traction, support and protection to enhance performance. However, since running usually forms some portion of most sports, most athletic shoes include design elements specifically aimed at enhancing running performance.
In general, an athletic shoe is divided into two general parts, an upper and a bottom unit which contains a sole. The upper is designed to snugly and comfortably enclose the foot. Typically, the upper will have several layers including a weather and wear-resistant outer layer of leather or synthetic material, such as nylon, and a soft, padded inner layer for foot comfort.
The bottom unit provides a broad, stable base to support the foot during ground contact. The sole must also provide traction, protection, and a durable wear surface. For example, the considerable forces generated by running require that the sole provide enhanced protection and shock absorption for the foot and leg. Also, it must have an extremely durable bottom surface to contact the ground, together with a shock absorbing midsole to absorb the considerable force to which the foot and leg are subjected during the repeated ground contact which occurs during running.
The typical motion of the foot during running proceeds as follows. First, the heel strikes the ground, followed by the ball of the foot. As the heel leaves the ground, the foot rolls forward so that the toes make contact, and finally, the entire foot leaves the ground to begin another cycle. During the time that the foot is in contact with the ground, it typically is rolling from the outside or lateral side to the inside or medial side, a process called pronation. That is, normally, the outside of the heel strikes first and the toes on the inside of the foot leave the ground last. During this process, the foot rolls about an axis of pronation which is generally positioned longitudinal to the foot and extends through the cuneiform bones of the foot. This axis of pronation may be located up to several inches above the bottom surface of the foot, and there is a similar axis of pronation when walking.
Similarly, the rapid weight, foot position, and direction shifts associated with playing certain sports, such as basketball and soccer, place tremendous stress on the player""s feet. To reduce the likelihood of injury and improve the player""s stability, maneuverability, balance, and control during these rapid weight or direction shifts, it is desirable for the forefoot portion of a player""s foot to move axially with respect to the heel portion of that foot. For example, when basketball players defend the goal and assume a fixed position on the court, they must often lean towards an approaching player while keeping their feet fixed. It is desirable for the forefoot portion of these players"" feet to remain fixed on the court surface, while their heels and ankles tilt toward their respective approaching players. Similarly, when an athlete lunges sideways, it is desirable for the forefoot portion of his foot to initially remain fully positioned on the playing surface, while the heel and ankle portions of the athlete""s foot tilt in the direction of the lunge.
The optimal shoe sole will facilitate these foot motions. Accordingly, it should support the foot along its entire longitudinal length, without interfering with the natural pronation of the foot while running, and flexibly decouple the forefoot and heel portions of the shoe from each other to facilitate respective axial movement of the forefoot and heel portions of the foot.
While most shoe soles support the foot, they do not provide adequate axial flexibility. For example, many midsoles and outsoles are monolithic longitudinal resilient structures extending from the heel to the toe of the shoe. The degree of stiffness of the structures determines the sole""s ability to longitudinally support a foot. The structures must be rigid enough to support a foot, but flexible enough to flex and account for the rolling motion of the foot while walking and running. In practice, providing a rigid enough monolithic sole to fully support a foot along its longitudinal length, significantly limits the axial flexibility of the shoe.
One known device for supporting the foot includes positioning a stiffening plate between the midsole and outsole of the sole. The stiffening plate is usually a generally planar surface constructed of a semi-rigid, or stiff, material such as woven carbon fiber, glass filled nylon, Thermoplastic Polyurethane (xe2x80x9cTPUxe2x80x9d), nylon, urethane, woven glass plates, and the like, that extends longitudinally from a heel portion to a forefoot portion of the sole. The plate improves support and stability to the foot, by limiting the flexibility of the sole along an axis transverse to its longitudinal length. Accordingly, the sole remains generally rigid along its length, thereby supporting the entire foot as it rolls from its heel to toe while running or walking. While a sole having a known stiffening plate may slightly flex axially about its longitudinal length, the degree of axial flexibility is generally not sufficient to prevent interfering with the natural pronation of the foot.
Structures that address the overall design of athletic shoe stiffening plates and their axial flexibility have been disclosed in prior art patents. For example, U.S. Pat. No. 4,922,631 to Anderie discloses using a longitudinal stiffening member positioned along the longitudinal centerline of the sole of a shoe. The member extends between a front sole portion and a rear sole portion, which are separated by recesses. As a result, the front sole portion can twist relative to the rear sole portion about the longitudinal axis of the stiffening member. However, this axis of rotation is positioned within the sole, several inches below the axis of pronation of the foot. Accordingly, when an athlete runs in such shoes having known stiffening plates in them, each foot will attempt to pivot about its axis of pronation, while the shoe pivots about the longitudinal axis of the stiffening plate. This displacement of the two axes with respect to each other results in several problems. For example, the foot may rub or slip within the shoe contributing to heel slippage, excessive friction heat build-up, and abrasion of the foot. Also, depending on how the foot interacts with the shoe, the mobility of the foot may be compromised, thereby limiting an athlete""s range and power.
In a more recent patent, the weight of athletic shoes is reduced by removing a portion of the sole adjacent to a central arch region and replacing it with a light weight arch support member spanning between an aft heel region and a forefoot region of the sole. See, U.S. Pat. No. 5,319,866 to Foley et al. While such arch support members may allow the removal of non-essential sole material, they do not axially decouple the heel portion from the forefoot region of the sole. Therefore, they do not improve the axial flexibility of the shoe, nor facilitate natural pronation.
Thus, despite the known prior art techniques, there remains a need for a light weight athletic shoe that facilitates natural pronation of a foot and axial flexibility while still fully supporting the foot along its entire longitudinal length.
The athletic shoe according to the present invention includes an upper secured to a sole having a heel portion, an opposite forefoot portion, and a stabilizing frame or member extending between these portions operably securing them to each other. The stabilizing member preferably includes a central portion extending above the heel and forefoot portions and is shaped to allow the two portions to move with respect to each other generally axially about a longitudinal axis above the heel and forefoot portions while enhancing the rigidity of the shoe along its length.
In one preferred embodiment, two stabilizing members are secured to the sole portions, and the heel and forefoot portions move with respect to each other generally axially about an axis of pronation of a foot wearing the shoe. One member is positioned on the medial side of the sole while the other member is positioned on the lateral side of the sole.
The central portion of each stabilizing member is generally c-shaped which extends between flat fore and aft sole mounting portions. The mounting portions lie in substantially in the same plane with each other, and the central portion extends upwardly and outwardly from the mounting portions, conforming with and adjacent to the upper.
The fore sole mounting portion of the medially mounted stabilizing member is preferably positioned so that it occupies a space below the first metatarsal head of a foot. It""s central portion sweeps upwardly and backwardly adjacent to the medial side of the foot so that it occupies a space adjacent to the arch area of the foot following a generally arcuate path to a turn-around point below the medial side of the ankle. It then sweeps downward so that the aft sole mounting portion is positioned under the heel on the medial side of the foot.
Similarly, the fore sole mounting portion of the laterally mounted stabilizing member is preferably positioned so that it occupies a space below the second and third metatarsal head of a foot. It""s central portion sweeps upwardly and backwardly adjacent to the lateral side of the foot so that it follows a generally arcuate path to a turn-around point below the lateral side of the ankle. It then sweeps downward so that the aft sole mounting portion is positioned under the heel on the lateral side of the foot. Each stabilizing member preferably includes a stiffening rib to enhance rigidity of the shoe in a direction horizontally transverse to the longitudinal axis of the sole.
When the foot of a typical runner wearing a shoe of the present invention contacts the ground along the lateral heel area, the heel portion and forefoot portions of the sole decouple or pivot with respect to each other such that they axially move with the foot about the foot""s axis of pronation. Similarly, during the rapid, weight and direction shifts associated with playing certain sports such as soccer or basketball, the athlete""s forefoot and corresponding forefoot portion of his shoe freely move axially with respect to the heel portion of his foot and shoe. However, the foot remains fully supported along its entire longitudinal length. Moreover, because the stabilizing members longitudinally support the arch of the foot, the need for heavy and durable sole material in the arch area is minimized, thereby resulting in a light weight and more economical shoe.
Various advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there are illustrated and described preferred embodiments of the invention.